Adjustable rotary counterbalance crank



7 Nov. 13, 1951 F, EATON 2,575,075

ADJUSTABLE ROTARY COUNTERBALANCE CRANK Filed Feb. 24, 1949 2 SHEETS-SHEET 1 Liz $1 at? Z Nov. 13, 1951 J. F..EATON 2,575,075

ADJUSTABLE ROTARY COUNTERBALANCE CRANK Filed Feb. 24, 1949 2 SHEETSSHEET 2 A)! If III 22- AA a g l a I] r FIZZ l Patented Nov. 13, 1951 S-IABEE RGT-ARY GRANK John Fitz-Eatb ,,rii1s a, 01415., assignor toBtlil'elieni Sulml'yJCo'inflany, a corporationof Dela=' Appiicatmmeebmamai, 1949, Serial No. 78,023 IfClhims; (01174 -591) This invention, relates to a improvements in:

counterbalance;- cranks, fore-power shafts}, and; is particularly. directed; to an improvement in coune terbalancing means ion-cranks for oil well cl'ri'llling and pumping equipment of h the specific typ'el wherein weight, elements are arranged to slide; along amadially extendingrcrankh-a'rm, ancbmeana are provided m c1amp.Itlie ,weight elements-E along,

the:- arm .atlvarying distances from the center or;

rotation of the crank, whereby a variable amount;

load and at the. same timewere soadaptedthatf theycould be moved to and fixed at" the axis" of rotation; where. their torq'tiz'e. efi'ect:'wouldf have zero. value; In the Troiit patentf arrangement? the. weights are attached 'to" the crank-arm" by meansQof bolts; the, heads ,off which" engage slots: inlthe edgesvoff'thecrankwarmi Theouteredges: of the crank'arm' and 'tlz'feibottomsliof"t'he weights." (when in their erect position) aremachine'd. to guide the weights; along the crank arm; and to" permit of; relativelyf'easy;sliding when .7 the Lcran'kt arm is in a horizontalposition and'tl'lefweightjto" be. adjusted is in itsverect position. The usual procedure, on weight; adjustment in the" Trout desi n is, to rotate the" crank" 'shafti until the crank arm is. in L one .of, its two" horizontal po's'i tions; and to temporarily lock the crank. armin' thisv position by meansTof'the" power" syste'ms': brake mechanism; Thenby looseningjthe bolts holdingthe uppermost "Weight to the'horizo'nta'l crank: arm this iweightmay be moved to its new position by pryingitwithla barit is thenre bolted in its .5 new'position, 'the' brakexisjreleasedf and th'e operation i s'rep'eated for the then ermostweight;by;rotatingjf't1ietcrankshaft l80 to bring the cranki'arm'intoits.. other horizontal position, whereby the secondWeight'now on-top maybe, adjusted." f Inthe larger sizes. of modern pjjmping units the counterbalance 'wei-ghts ref quired'may be' OftITBiOIdGFOf "6000 pounds each; and the moving thereoffmanua'lly. with a" Dr bar in j the hands of ia workman forced" t'b". stand" onsome iportionof the apparatus'innrder to work tlrebar isattended :by; an elementof .dangefl andf isHkarduOus'andi time consuming"; 7 My) invention" thlerefon ;1re's j in:a n:: improvement ifori the Trout;

2,. type of: counterbalanceecrank-for oil well arming and pnmning eqnipment' designedtofreduce the time and labor required to reloalance the. unit,v andptoreduceto a minimum the danger of iiiin so doing:

It is therefore the'hpriinary .objectrof fii'y invention, to constrnet'. a1 counterbalance" 'erahli' arm for Oil weli'drilliilg andpllrnpifigequii inefiti having the weights thereof adaptedtovbe. slidably" adiiistable. alongmopposite edges" tli'e'rebfi the plane offrevol'ution, andawlier'ein'lthef saidadj'ustej ment' is readily and ifieieritly made" to both said" weights-when, the. crank armis in either one' 'oi its{ twosubstantially; horizontalriositiiiris'.

ItliSfa fili'the'robjebtwf my inventiofi'to'pro Vida-a counterbalance crank" am: having? support rails ,tliereonl for the support. of fslidably' adj fist= alile." weights; so arranged? that whether; the? weight'sf 1'70 be adjusted are ini'anie'reet or in a pendant position they maybeequallyreachly' and ero e-nay moved: 011,; adjusted" to," and clambed toItheii' respectiveisupportrail.

It. is. another" object of my. invention to have" the a sup ort rails j of my improved"counterbalanee crank" in 'its"preferredf'orm to beremovablyat tabhdto the armthereorfand tohav ethe support"rai1s,- thereof? comprise flat" rectangular bar's disposed" inf parallel "spaced'f relation alofig each edge of tliesaidiianli armiboth saidicranl z" arm and I said support rails ying flatwise with respect: to" tlie plane ofrevoli1tio'n of tlrecra'nk armQWh'ei'QIoy tl'i bearin means oftheweigiits engage; both'"edgies of. their respective support? rails; and Ttlie. weight clafn'p, rfie'an's engage b'b'th It is another ob'jedt'io'f' my ifiventiofitdprovi'def a1 erankoperated" ra'cli'-and-piiiion means" for readily and efii'ei'el'itlj'lfcontrbllifigitfiePositioning" o'fjthe' we'ightsfalongllif support rails of "my roved'counterlialancet-cranmp Itiis' anotlzieriobject" of mytinventi'orr to sod sign the clamping? element's that normally hol'd my counterbalanceweiglits iiioperatinyposition" that; wliefii'n the" loosened'eonditionforadj iist- I; ingjtll'efweights, jthe" clampingfeleinents "are freed o ftun'clue" clampingifriction by reason" ofan-'- irrherent elasticityfestaiblished in thestructural f d'e signfofftlie assembitfweiglitss It is? still anotl'ierfobj eet of. invention to tions, and is shown with the front half of the up per weight removed to better disclose detail structure,

Fig. 2 is a view looking upward at the bottom of the unit as shown in Fig. 1, 1 v

Fig. 3 is an end elevation of the left end of the unit as shown in Fig. 1, having a partial section thereof, I

Fig. 4 is an elevation of the right end of the unit as shown in Fig. 1, havin a partial section thereof, and, I r

Fig. 5 is a sectional view taken along the line 5-5 of 'Fig. 1 as seen in the directionof the arrows 5-5.

Referring now to the drawings, and more par ticularly to Fig. 1, the numeral |ll designates the complete ensemble of a counterbalance crank unit embodying the preferred form of my inven-- tion.

The counterbalance crank unit It] comprises two main sub-assemblies-j-the crank arm assembly and the two counterbalance weight assemblies l2.

The crank arm assembly II is comprised of the crank arm I3, and the support rail assemblies l4.

The crank arm I3 is preferably a gray-iron casting with the conventional finished keyed shaft bore l5, and the finished keyed wrist-pin holes Hi. The shaft bore i5 is adapted to be secured to a power shaft (not shown) normally rotated by a suitable source of power. The shaft bore l5 may be surrounded with a solid-hub (not shown) and pressed on the power shaft in a well known manner, or it may have a split-hub H as shown in Fig. 1 extending to the outer end of the crank arm I3 and be clamped on the power shaft as hereinafter described. The wrist pin holes l6 (four in number as shown in Fig. 1) permit the attachment of the wrist pin bearing (not shown) at various distances toward or away from the crank shaft bore l5 depending upon the desired pumping stroke-length. Legend'numerals l8 may be provided opposite each wrist pin hole I6 indicating the pumping stroke-length provided by using the respective holes for the wristpin hearing. At both end of the crank arm I3 and at opposite edges thereof are cored bolt-holes |9 to be hereinafter referred to in more detail. Extending substantially full-length on each side of the crank erably 'of rolled steel, rect'ang'ular'in'cross section, and arepreferably jig-welded'as at 2'4 and 25 into slots 26 cast in the hanger castings 23. The hangeicastings 23 are providedwitha cored bolt slot:

21 cast therein. The bolt slots 21 are provided on their inner upper surface with recesses 28 to re-' ceivethe bolt heads and prevent them from turning when manipulating-the nuts thereon. The inner'e'nd of this" bolt slot'Zl is provided at its outer semi-circular edge with an integral conical projection 29 designed to project into a matching conical recess 39 formed at the outer ends of the cored bolt holes l9 in the crank arm l3 (see Fig. 3). The purpose of these conical projection fitting into a matching recess in the crank arm is to position the rail assemblies l4 orthe crank arm l3 and to prevent lateral displacements thereof when the support rail assemblies l4 are fastened means 3| and-32 (see Fig. 1).

l in the outer end of the crank arm i3.

in place on the crank arm [3 by the fastening The fastening means 3| function to fasten the outer ends of the rail assemblies l4 to the outer end of the crank arm l3 and they comprise the bolts 33 extending through the cored bolt slots 2'! in the hanger castings 23, and through the cored bolt-holes l9 The fastening means 3| are completed by the nuts 34 and lock washers 35. The fastening means 32 (see Figs. 1 and 4) performs a dual functionit fastens the inner ends of the rail assemblies M to the inner end of the crank arm I3 and it acts to clamp the crank arm l3 to its power shaft (not shown) by its clampingaction on the shaft bore |5. The fastening means 32 comprises the two bolts 36 and 31 having right and left hand threads respectively, the turnbuckle nut 38, and the lock nuts 39 and 40. The turnbuckle nut 38, and the lock nuts 39 and 40 are suitably tapped for the bolts 36 and 31.

It is obvious of course that when a pressed-on type of crank arm is used, as noted hereinabove,

that the fastening means 3| may be used at the inner ends of the rail assemblies to replace the turnbuckle type 32 not then necessary.

With the split type of crank arm l3 as shown in Fig. 1 the rail assemblies M are assembled to the drawing the bolts and their associated parts to-' gether toa simultaneous seating upon the crank arm I 3. The nuts 34 and lock washers 35 are then placed on the bolts 33 andtightened to complete the assembly.

The two counterbalance weight assemblies l2 are each comprised of the two half-weights 4|, bolted together by means of an outer pad clamp bolt 42 and four rail clamp bolts 43 each provided with nuts 44 and washers 45; weight rollers 46 mounted on said rail clamp bolts 43; and, pinion assembly 41 (see Fig. 5).

The half-weights 4| are identical and are preferably made of cast iron. Each half-weight 4| is provide-d with cored bolt hole 48 for the pad clamp bolt 42 and the rail clamp bolts 43. The outer end of each cored bolt hole 48 is provided with the recesses 49 and 50 (see Fig. 5). The

recesses 49 are adapted to fit the head of the bolts 42 and 43 to prevent their turning when being manipulated with a wrench, and .the recesses 50 are adapted to provide clearance for the' use of a socket wrench (not shown) and centerline arelthe raised sp cin pass having tneraces 'sz'rsee' Figs. rand '3)"Wh'ich are in mutuall engagement when the halfweights 4! are bolted together by the padcl'a mpboltfi'l Also the inner side of each nan-wei hts! "on the vertical center hues of the railclampbolts 43and' spacedtherebetween in each case are the rail clam pads 53 having races 54"(seeFig's: lanes) which are in parauei spaced reunion one with an other. when the hnnwa nts 4| are bolted to' g'ethei' by the pad damp bolt 42: When' ass f bled iii the complete counterbalance crank um l a andready for use thefaces 51s 'of'the opposes an clam pads in intiriiate 'enga'ge Ifi'efit "with'opp'osite races of their adjacent int'er= ve' n'g rail bar 22 byreason' of the clamping ac tionof the four rail "clamp bolt 43 in their tight iied condition, the intervening distance their existi between the races 5a is the actual mien;

ness of the rail bar 22. However; when the bolts 43 are loosened it is desirable that a slight clear since automatically exist between the rail blar'a'rld' the faces 54 in order that the Weights-may be readily m'oved without undue frictional restraint. Tdaccomplishthis desirable feature the di'iiei idea in height between'th'e faces 52 of the spacing padsfil and the faces-54 of the rail clamp'p-adsfie- E iss'o adapted that when in its assembled post'- tionwith th'e'pad clamp bolt 42 tightened and free ofothertension' by reason of the rail clamp bolts 43;; being "loosened the's'paceddistance be tween the'faces'fit is slightly greater than when" they are drawn into engagement with the rail b'ar 22 'bythe tightening of thebolt's "$3. This untightened clearance may be 'of the-order ofonethirty second of an inch for eachside ofthe bar"a' clearance well Within the 'operableelastic limits ofthe parts strained When the bolts 43 with respect to the depressed surfaces 55 (see 5) of "the half-weiglitsii. Ptecesse's 55 (see F igz' 1 in the half-Weights 4| provide-adequate diamet'ral clearancesabout the outer ones or the rollers 46: A

1 fine 'opir'iion'assemblyi'i (seer'igt ecmpr-ises the piniori'i'l, bushing-bearings 58, and'sn'ap spring retaining rings 59 The pinion 5'! is preferably of cast "steel having:

a -central portion with cast gear teeth 65); outweirdly extending shaft bearing portiohslil, andsli'aft end portions 62 adapted for engagement with a suitable hand crank socket wrench (not shown) Between thebearing --portions 6! and the endportions 62 the shaft extensions'a're adapted with grooves 63'for snap spring retaining rings 59. For mounting the pinionassiri'bly 41 the halfwei-ghts'"4'l are provided with the cylindrical recesses '64 adjacent the inner edge thereof on its vertical centerline; and eachretesset is further provided with an inner sl-tour: dered'recess65 (see-Figs; I and 5).- The inner recesses 55 are adapted to- }be slightly ierger diameter than the outside" metercrthe st gear teeth 'iiflwherebythe- "on ti f serted' orwithdrawnithe ough fisee-Fig; 1- The recesses *BVeZreadapt'eiitb receive the bush bly're'c'ess 64 thereof is provided a position index boss. The index boss 66 is intended to cooperate with a respectivescale 61 graduated along the adjacent serratedflanges 20. The scale 61 may be marked with legendnumbers 68 having known counterbalancin'g values which may be chosen selectively for use in adjusting the counterbalance weight assemblies l2 to their desiredposition.

Each "of the half weights 4| are provided with a coredhole 69 on the vertical center line thereof adjacent the pad clamp bolts 42. This cored hole is provided for lifting the weights I2, and as-' sembled unit ilif and'when necessary.

The counterbalance weight assemblies 12 are readily assembled to or dismounted from the crank arm assembly H as follows:

With the crank'arm assembled H as herein before describedand placed in a horizontal position; one of the counterbalance weight assemblies-l2 completeexcept for the two inner rail clamp bolts43 and the pinion assembly 41 may be lifted, using the lifting holes 69, andth'en set in position on the uppermost ra'il bar 22 about midway of its ends. Bottom weight rollers 46 may then be inserted between the two half-' weights 4!, andbetween the rail bar '22 and the upper serrated flange 20 of the crank arm. The rollers 46 are inserted one at each end of the weights and each may be pushed inward to alignment position with the lower cored bolt holes 48. In order to prevent the rollers 46'going past'the holes 48, lugs 10 are provided cast integral with the half-weights 4| adjacent each lower bolt hole 48 (see'Fig. 1). The lower rail clamp bolts 43 may ne'xt'be inserted from the back face of the counterbalance weight assembly I2 through the'rollers '46, and all the rail clamp bolts 43 with their associated nuts 44 and washers 45 may be tightened in place. The assembly of this counterbalance weight assembly l2 to the crank arm assembly H is completed by installing the pinion assembly 41 as hereinbefore de scribed. The crank arm assembly together with its first counterbalance Weight assembly l2 clamped thereto is then revolved about its shaft bore I5, and the second counterbalance weightassembly i2 is assembled thereto in the manner just described for the-first one.

The operation of adjusting the weights to a desired position when in the field and in use will now be described. The counterbalance crank unit it is rotated to have its crank arm [3 in either one of its two horizontal positions, as may bemost convenient, and is so locked by means ofthe power systems brake throughout the whole adjusting operation; Both weight assemblies 12 may be adjusted from this one locked position bythe operator standing on the ground; facing the crank; and clear of the *unitwhile-moving the weight assemblies I 2 -'t"o *their new-positions.-

7, When therail clamp bolts 43 are loosened the rail clamp pads 53 free themselves from intimate contact with the rail bars 22, as hereinbefore described, thereby eliminating friction at these surfaces. The operator using a hand crank socket wrench applied to the squared exposed end portion 62 of the pinion 51 is able to move the weights l2 readily, and under constant control, by reason of the crank driven pinion-andrack mechanism in combination with the rollers 46 supporting the weights. The ease of operation together with the ability to do all adjusting with one position of the crank arm reduces the time and labor required, as well as making a safer operation. The adjustments made, and the clamp bolts retightened, the counterbalance cr'ank unit It is again ready for use.

It may be further noted that I have provided rack'teeth 2| the full length of the crank arm l3 although the pinion normally moves only in the middle section of the rack in the course of transferring the weight assemblies 12 from maximum to minimum effective position. In the event the pinion 5! is inoperative due to breakage, excessive rusting, and et cetera, it may be removed and the weight assemblies l2 moved by means of a bar in conjunction with the rack teeth 2| which will serve as a fulcrum for the end of the bar. In conjunction with such emergency use of a bar I provide a prying space H (see Fig. 1) between the hanger castings 23 and the weights l2 in order that the weights may be pried away from an extreme end position, and the rack teeth near the ends of the crank arms l3 may then be used as fulcrums for the pry bar, to thus move the weights l2 toward the middle of the crank arm I claim:

1. In a counterbalancing device for power shafts, the combination of a radial arm adapted to be mounted on a shaft and provided with serrated edges along both sides thereof in the plane of revolution, rail bars spaced from parallel to and located in substantially vertical alignment with said serrated edges, counterweights supported on and adapted for slidable engagement with each of said rail bars in both an erect and a pendant relationship with respect to said radial arm, means for clamping said counterweights immovably with respect to said rail bars, and crank operable pinion means mounted in each of said counterweights in operable engagement with their respective adjacent serrated edge.

2. In a counterbalancing device for power shafts, the combination of a radial arm adapted to be mounted on a shaft and provided with serrated edges along both sides thereof in the plane of revolution, rail bars spaced from parallel to and located in substantially vertical alignment with said serrated edges, counterweights supported on and adapted for slidable engagement with each of said rail bars in both an erect and a pendant relationship with respect to said radial arm, means for clamping said counterweights immovably with respect to said rail bars, means effective to permit free slidability and secure clamping of the counterweights when the said clamping means are respectively loosened or tightened, and crank operable pinion means mounted in each of said counterweights in operable engagement with their respective adjacent serrated edge.

3. In a counterbalancing device for power shafts, the combination of a radial arm adapted to be mounted on a shaft and provided with serrated edges along both sides thereof in the plane of rotation, rail bars spaced from parallel to and located in substantially vertical alignment with said serrated edges, means for attaching said rail bars to the radial arm, counterweights supported on and adapted for slidable engagement with said rail bars in both an erect and a pendant relationship with respect to said radial arm, means for clamping said counterweights immovably with respect to said rail bars, and crank operable pinion means mounted in each of said counterweights in operable engagement with their respective adjacent serrated edge.

4. In a counterbalancing device for power shafts, the combination of a radial arm adapted to be mounted on a shaft and provided with ser-' rated edges along both sides thereof in the plane of revolution, rail bars spaced from parallel to and located in substantially vertical alignment with said serrated edges, two-part counterweights having their outward portions in united mutual facial engagement comprising fastening means for maintaining said facial engagement, crank operable pinion means mounted in each of said counterweights in operable engagement with their respective adjacent serrated edge, and havin bearing means in each of said counterweights engaging the inner and outer longitudinal edges of their respective said rail bars for slidable adjustment of the counterweights thereon whereby said adjustment may be made in both an erect and a pendant relationship of said counterweights with respect to said radial arm, and means for clamping inner surfaces of said counterweights on the respective opposed parallel faces of the said rail bars.

5. In a counterbalancing device for power shafts, the combination of a radial arm adapted to be mounted on a shaft and provided with serrated edges along both sides thereof in the plane of revolution, rail bars spaced from parallel to and located in substantially vertical alignment with said serrated edges, two-part counterweights having their outward portions in united mutual facial engagement comprising fastening means for maintaining said facial engagement, and having bearing means in each of said counterweights engaging the inner and outer longitudinal edges of their respective said rail bars for slidable adjustment of the counterweights thereon whereby said adjustment may be made in both an erect and a pendant relationship of said counterweights with respect to said radial arm, means for clamping inner surfaces of said counterweights on the respective opposed parallel faces of the said rail bars, means effective to permit free slidability and secure clamping of the counterweights when the said clamping means are respectively loosened and tightened, and crank operable pinion means mounted in each of said counterweights in operable engagement with their respective adjacent serrated edges whereby said counterweights may be manually adjusted when the radial arm is in a substantially horizontal position.

6. A counterbalance crank arm for power shafts, comprising a radial arm adapted to be mounted on a power shaft and to support a wrist pin and provided with serrated edges along both sides thereof in the plane of rotation, rail bars spaced from parallel to and located in substantially vertical alignment with said serrated edges, two-part counterweights having their outward portions in united facial engagement comprising fastening means for maintaining said i ee i eesageie nt area tremble pini n m ans mo e n e ch o nt i ht e se ar- 191 en a m n w th thei r s ect ve adie e serrated edge, and having roller bearing means aimed nzgeeh t ais twili h -t ht engagin th inn ran uterio situd eal edg at sa ra l bars for sl dable a iiis ment Qf h cou erie t th eqn lwhcr b v aid d u men a smade both easies -and a i? a-nt re ationship with respect to .lsaidtradial and comprising operable fastening meansleffecti e for clamping i nersufiaw of sa counte wei. i n h rett n O ed aral el fa e 9 the said rail rs and e er ent ne said mi l b a ings in their operable relation whetherzsaid qu r e s a n lamped undergra relationship with; said railbarsl 3 -7. A counterbalance crank arm for power shafts, comprising a radialarm adapted .to be mounted on a power shaftand to support awrist mounted .in .each. of said counterweights engaging the inner .and outer: longitudinal ledges of said rail barsufor.slidableadjustment,ofthe counterweights thereon whereby said adjustment may be made in both an erect and a pendant relationship with respect to said radial arm, and comprising operable fastening means effective for clamping inner surfaces of said counterweights on the respective opposed parallel faces of the said rail bars and for supporting said roller bearings in their operable relation whether said counterweights are in clamped or unclamped relationship with said rail bars, and means effective to permit free slidability and secure clamping of the counterweights when the said clamping means are respectively loosened or tightened.

8. A counterbalance crank arm for power shafts, comprising a radial arm adapted to be mounted on a power shaft and to support a wrist pin and provided with serrated edges along both sides thereof in the plane of revolution, rail bars spaced from parallel to and located in substantially vertical alignment with said serrated edges, two-part counterweights having their outward portions in united facial engagement comprising fastening means for maintaining said facial engagement, and having roller bearing means mounted in each of said counterweights engaging the inner and outer longitudinal edges of said rail bars for slidable adjustment of the counterweights thereon whereby said adjustment may be made in both an errect and a pendant relationship with respect to said radial arm, and comprising operable fastening means effective for clamping inner surfaces of said counterweights on the respective opposed parallel faces of the said rail bars and for supporting said roller bearings in their operable relation whether said counterweights are in clamped or unclamped relationship with said rail bars, means effective to permit free slidability and secure clamping of the counterweights when the said clamping means are respectively loosened or tightened. and crank operable pinion means mounted in each ,ofsaidcounterwihts in operable engagement with their respective adjacent serrated edgeswhereby said counterweights may be manu ally adjusted when the radial arm is inla sub stantially horizontal position. v

merits, detachable fastening means for mainni s sai as en a -e im rw t supported on and adapted for slidable engage;- ment with said rail bars in both an erect and a pendant relationship with respect to said radial arm, means for clamping said counterwe ht immovably with respect to ,said rail' bars, and crank operable pinion means, mounted in each of said counterweights in operable engagement with the r terat e ad acen Serrated d e- 10. s. counterbalance crank arm for power s afts comp sin a radial a adapted tabs mou ted en a mwe she and to Su po ts s pin and provided with serrated edges along both sides thereof in the plane of revolution'having attachment abutments :at'each' end thereof, fail bar spa ed om time i a d locat d. n

stantially vertical alignment with said serrated edges comprising end .attachment means, adapted in er. fix d-en agement sa s pm t d teqhab ;taste i meeesii h ie as-a fixed engagement, counterweights supportedpn and adapted for slidable engagement with said rail bars in both an erect and a pendant relationship with respect to said radial arm, means for clamping said counterweights immovably with respect to said rail bars, crank operable pinion means mounted in each of said counterweights in operable engagement with their respective adjacent serrated edge, and means effective to permit free slidability and secure clamping of the counterweights when the clamping means are respectively loosened or tightened.

11. A counterbalance crank arm for power shafts, comprising a radial arm adapted'to be I mounted on a power shaft and to support a wrist pin and provided with serrated edges along both sides thereof in the plane of revolution having attachment abutments at each end thereof, rail bars spaced from parallel to and located in substantially vertical alignment with said serrated edges comprising end attachment means adapted for fixed engagement with said abutments, detachable fastening means for maintaining said fixed engagement, counterweights supported on and adapted for slidable engagement with said rail bars in both an erect and a pendant relationship with respect to said radial arm, means for clamping said counterweights immovably with respect to said rail bars, crank operable pinion means mounted in each of said counterweights in operable engagement with their respective adjacent serrated edge, and fastening means effective to simultaneously fix the radial arm to its shaft and to fix one end of each of said rail bars to said radial arm.

12. A counterbalance crank arm for power shafts, comprising a radial arm adapted to be mounted on a power shaft and to support a Wrist pin and provided with serrated edges along both sides thereof in the plane of revolution having attachment abutments at each end thereof, rail bars spaced from parallel to andlocated in substantially vertical alignment with said serrated edges comprising end attachment means adapted for fixed engagement with said abutments, detachable fastening means for maintaining said fixed engagement, counterweights supported on and adapted for slidable engagement with said rail bars in both an erect and a pendant relationship with respect to said radial arm, means for clamping said counterweights immovably with respect to said rail bars, means effective to permit free slidability and secure clamping of the counterweights when the clamping means are respectively loosened or tightened, and crank operable pinion means mounted in each of said counterweights in operable ,engagement with their respective adjacent serrated edges whereby said counterweights may be manually adjusted when the radial arm is in a substantially horizontal position.

13. A counterbalance crank arm for power shafts, comprising a radial arm adapted to be mounted on a power shaft and to support a wrist pin and provided with serrated edges along both sides thereof in the plane of revolution having attachment abutments at each end thereof, rail bars spaced from parallel to and located substantially vertical alignment with said serrated edges comprising end attachment means adapted for fixed engagement with said abutments, detachable fastening means for maintaining said fixed engagement, two-part counterweights having their outward portions in united mutual acial engagement comprising fastening means for maintaining said facial engagement, and having bearing means in each of said counterweightsengaging the inner and outer longitudinal edges of their respective said rail bars for slidable adjustment of the counterweights thereon whereby said adjustment may be made in both an erect and a pendant relationship of said counterweights with respect to said radial arm, means for clamping inner surfaces of said counterweights on the respective opposed parallel faces of the said rail bars, means effective to permit free slidability and secure clamping of the counterweights when the said clamping means are respectively loosened and tightened, crank operable pinion means mounted in each of said counterweights in operable engagement with their respective adjacent serrated edges whereby said counterweights may be manually adjusted when the radial arm is in a substantially horizontal position, and fastening means effective to simultaneously fix the radial arm to its shaft and to fix one end of each of said rail bars to said radial arm.

JOHN FITZ EATON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 447,607 Gleason Mar. 3, 1891 1,742,552 Manning Jan. 7, 1930 1,770,601 Baker July 15, 1930 2,123,679 Mahan July 12, 1938 

